Protein adhesive compositions

ABSTRACT

An adhesive composition having particular utility for the manufacture of laminated cellulosic products wherein one component is an aqueous alkali-dispersed protein and the other component is an oxazolidine, e.g. (5-hydroxymethyl-1-aza-3,7dioxabicyclo(3,3,0)octane).

Umted States Patent [151 3,640,740 Stephan et al. 1 Feb. 8, 1972 [54] PROTEIN ADHESIVE COMPOSITIONS Referemes Cited [72] Inventors: John T. Stephan, Longview; Alex James UNITED STATES PATENTS Seattle wash- 2,448,890 9/1948 Johnston .260/307 F [73] Assignee; Comma-kg] Solvents Corporation, New I 3,408,198 10/1968 Reynolds et al. ..96/ l l 1 York, N.Y. Em M L b v Primary minerorris ie man [22] filed: 1969 Assistant Examiner-T. Morris 21 App] 1 1 7 Attorney-Howard E. Post and Robert H. Dewey [5 1 ABSTRACT [52] US. Cl ..106/l38,106/154, 156/317 [51] lnLCl. ..C08h7/00 adheswe composmon having particular utlhty for the [581 Field ofSearch ..260l307 F, 6; 106/124, 138,. manufacmre laminated cellumic Pmucts wherein one component is an aqueous alkali-dispersed protein and the other component is an oxazolidine, e.g. (S-hydroxymethyl-laza-3,7-dioxabicyclo[3,3,01octane).

5 Claims, No Drawings PROTEIN ADHESIVE COMPOSITIONS BACKGROUND OF THE INVENTION This invention relates to protein adhesive compositions. In a particular aspect it relates to alkali-dispersed protein-oxazolidine combinations for the manufacture of laminated cellulosic products. v l

ymethyl-l,3-propanediol (T), or 2-amino-2-ethyl-l,3-

1 propanediol (B); Other oxazolidines are known in the art but generally they are less satisfactory than the oxazolidines of the 1' l present invention..

The use of adhesives to'prepare laminated,celliilosic' products, e.g., plywood or paper products, is an old, wellknown process and many different adhesivesha've been'suggested. Presently, alkaline-dispersed protein adhesivesland low temperature-curing phenol-and 'resorcinol-formaldehyde' resins are in widespread use.

Soybean protein in an aqueous, alkaline dispersion, has'long casein and soybeanprotein. The alkaline material and the been in use as an: adhesive forthe manufacture of plywood; I

but it does not have the watereresistancethathassharacamount used to effectprotein dispersions is known in the art A and the prior art practice is suitable for the practice of this in- 1 vention. As is generally recognized, a high proportion of alkaline' materialwith respect to the protein can have a degradationjeffect" which can render the protein nongelling and inefterized the more recently employed hot pressphenol-formak dehyde resin adhesives. Bloodprote'inais in widespreadmse,

but supplies arelimited and it is comparatively highpricedg'" above about 160 F. This enables the formulation of alkaline aqueous adhesive solutions which gel:upon the. .application of heat. Such adhesives cure rapidly at-elevated temperatures hesives based on these'materials set by-a simple drying'out .fective as an adhesive. Accordingly, only sufficient alkaline I j material to 'effectthe protein dispersion should be employed, v20. Blood has the advantage over-soybeanprotemm-thatrtsaqua ous solutions areinherently thermosetting atztemperatures asis known in theart, ,[The adhesive combination of this invention is especially 'suitable for use in manufacturing laminated cellulosic articles,

, such as laminated timbers, plywood and paper articles, par- "'25 and have excellent water resistancei On the contrary,.casein 1 or soybean protein is thermoplastic and alkalineaqueous ad 1 procedure and/or chemical reaction.- Such solution's do not ordinarily gel on one application of heat.

A need therefore exists for. upgrading soybean and caseinbased protein adhesives toperform a thermosetting function comparable with blood protein or thermosetting synthetic resin adhesives.

SUMMARY OF THE INVENTION wherein R is ethyl or hydroxymethyl possesses. the rapid setting and water resistance of proteinadhesives. When-R is ethyl, the -oxazolidine is 5-ethyl-l-aza-3,7-dioxabicyclo[3.3.0}octane, which hereinafter will be referredto'as oxazolidine E: when R is hydroxymethyl, the oxazalidine is 5 hydroxymethyl l aza 3,7 dioxabicyclo [3,3,0]octane,

which hereinafter willbe referred to as oxazolidine T.

DETAILED DISCUSSION The proportion of protein to oxazolidine in the composition of the present invention is not critical; Preferably, however,

they are present in a ratio of about-3 m about parts of protein (dry basis)- to 1 part by weight of oxazolidine. Generally a high proportion of protein leads to longer working time. The bicyclic oxazolidines-used in the'adhesives of the present invention may be prepared according to the method 'of Murray Senkus, J. M. Chem. Soc. 67,.15l5-I5l9(l945) or that of William B. Johnston, U.S. Pat.- No. 2,448,890. Generally these compounds are made by the reactionofFZ 1 ticularly by the separate application process described in US. Pat. No. 2,015,806. In this process one component is applied to one surface and the second component is applied to the othersurface. The two surfaces are joined, pressure is applied,

and the components react to form a powerful bond. It is also suitable to .premix the two components and apply the mixture to the surfaces to' be joined. However, the high reactivity of the two components may give a short working time.

In assembling materials to be laminated, it is customary to subject themto bonding pressure in a suitable press, which can be operated at ambient temperatures, or heated to the .desired temperature, e.g., to as much as 300350 F. The

amount of pressure can be varied, but generally the pressures used in the art are suitable, e.g., pressures of the order of 100-200 p.s.i. Pressure generally is employed to secure a good bond'through intimate contact of surfaces.

The components. of the adhesives of the present invention react readily atambient temperature, e.g., from about 68 to about 110 P, so the application of heat is not required.

Elevated temperatures promote more rapid setting, however,

and can be. used after assembly of the article when high-speed reactivity is desired. Temperatures generally in the range of from about 1 10 to about 350 F. are suitable.

The. above invention can be better understood by reference to the following examples. However, these examples are only for the purpose of illustration and it is not intended that the invention be limited thereby.

EXAMPLE 1 An alkaline aqueous dispersion of protein was prepared by mixing-50 g. of casein (80 mesh, Argentine lactic grade) with 100 ml. ofwater and 5 g. of 50 percent sodium hydroxide solution. The casein solution thereby obtained was a typically fluid', ta cky material. The solution was divided into two portions.-To one portion 5 percent by weight of oxazolidine E was added, and to the other 5 percent of T. With E," gelation of the protein occurred in about 5 minutes, and with T gelation occurred in about 20 minutes. When a freshly mixed sample of the casein solution with 5 percent T" was heated, gelation occurred promptly when the temperature reached about 140 F.

EXAMPLE 2 This experiment was performed to demonstrate the reactivitybetween the-oxazolidine T. and soybean protein. In this series ofexperiments, five layers of fir veneer, 16 inch, were assembled toformalaminate. The soybean protein dispersion was prepared from commercial soybean protein, 400 g., and dispersed in l,600 g. of water with 50 percent sodium hydroxmoles of formaldehyde with 1 mole of -2'-amino-2-hydrox- .:idesoluti0n, 57g; The soybean protein dispersion was then mixed with 1 percent by weight of oxazolidine T to give a proportion of protein to T" of about 20:1 and applied to the veneer layers at about 50 lbs/1,000 sq. ft. of single glue line.

An aliquot of 100 g. of the solution was mixed with 5 ml. of

- oxazolidine E" (5.35 g.), to give a ratio of protein to E of In two experiments the assembly times were minutes and minutes at 150 p.s.i. pressure which resulted in a normal dry bond.

EXAMPLE 3' A dispersion was prepared by mixing 100 g. of a commercial soybean flour with 400 g. of water (70 F.) and l 1.4 g. sodium hydroxide. Five grams oxazolidine T per 100 g. of the wet adhesive mix was added to provide a ratio of about 4:l of protein to T, and the fluid mixture was heated in a water bath. A firm gel developed when the adhesive temperature reached between about 168 F. and 175 F. In the absence of T, no gel developed on heating to 175 F. or after holding at 212 F., for extended periods.

The above experiment was repeated except that 10 percent sodium silicate (wet glue basis) was mixed with the soybean protein. Then 1 percent of T" dissolved in water was added to the mixture to provide a ratio of about :1. A firm gel was about 3.4:] and a second aliquot of 100 g. was mixed with 5 g. of oxazolidine T" to give a ratio of about 3.6: 1.

The solution containing E" gelled in l5 minutes at 70 F.

, The solution containing T" gelled within 2% hours at room produced when the mixture was heated to 180 to 190 F. This I EXAMPLE 4 The following experiment was conducted with a soybean flour dispersion prepared as follows:

soybean flour 400 g. water l680 g. NaOH (50% solution) [22 g. Total 2202 g.

The above colloidal mixture had a ratio of 15 g. of NaOH solid per 100 g. of soybean flour.

temperature, but did not gel when heated to 210 F. This indicates that gelatinization temperature can be controlled by adjusting the ratio of caustic soda to soybean flour, as well as the quantity of oxazolidine.

EXAMPLE 5 An alkaline soybean dispersion was prepared in accordance 1 with example 4 except that only 55 g. of 50 percent aqueous sodium hydroxide solution was employed. giving a final con centration of 6.7 g. NaOH per g. of soybean flour.

To a 100 g. aliquot of the above aqueous mixture was added 5 g. of oxazolidine 'l" to give a ratio of 3.7: 1. One sample of this solution gelled at l50 F. and another gelled in l% hours at room temperature.

A typical corrugated paper laminate was prepared using the above mixture containing T at a press time of 20 seconds at 300 F. The resulting laminate exhibited 100 percent bond even after a 6-hour soak in water.

We claim: 1. An adhesive composltlon comprising a combinatlon of an alkaline casein or soybean protein solution and an oxazolidine represented by the formula 

2. The adhesive combination of claim 1 wherein R is ethyl.
 3. The adhesive combination of claim 1 wherein R is hydroxymethyl.
 4. The composition of claim 1 wherein said protein is casein.
 5. The composition of claim 1 wherein said protein is soybean protein. 